Circuit breaker employing a pair of arc chutes



JIuly 22, 1952 G. A. BURNHAM CIRCUIT BREAKER EMPLOYING A PAIR OF' ARGCHUTES Filed Nov. 10, 1949 SQA y pa'city'iof thebreakerfit wouldbene'ceslsury, increase the'i'pressure and theintensity ofl the ga/sblast.y if it is impraeucaito nicreas'ethe gas pressure',A the size ofthejblastpassage orth'e Patented July 22, 1952 STATES PATENT y C.CIRCUIT Bananen EMPLOYING A` PAIROF i ARC cHU'rEs f i' George-.Burnham,l Saugus, Mass., assigner to Allis-Chalmers ManufacturingCompany, Mil-y Waukee, Wis., acorporation ckfvfrDclaware I.Application:November 10, 1949 lVScrial'eNo...126,531.2

, 1 i i A'Iihis :invention `relates .to Ycircuit interrupting devices,and kmore particularly to arc extinguishing means for use in connectiontherewith.

V`In the construction and operation .of circuit ,interrupters it visfrequently necessary to provide vmeans for extinguishing quickly the arewhich is ldrawnbelniveen separable arcing contacts. This garnis usuallyyblown byblowout means, .such as :anjair blast, into Aan arc chute whichis arranged `'to quench the arc byrlengthening it, cooling it, or

otherwise.` 4 ,y The'int'errupt'ing capacity of avfcircuitybreaker y`inahigh voltage circuit de nds tov a greatfexf tent on the `'circuitcharacte'rls'tics relatingto the rate jof increase of yrecovery voltageWhenthe of the lgap. To increase the v.i,n tf-:lrrupting'l-ca- `type ofgas passage or passages maybe variedV to ,provide forl .greater vgasvolume or u greater. inter; vruptlngability. Such changes, howevek'i'isuall'y 'result in either a inoreexpensivefor `larger breakert I 1.1f "-"In accordance with the f invention {clairned a `fluid lblastcircuitl interru'pter`l is provided lwhich lcomprises Aapair/of arcingcontacts Vmountedwith:

in an arc .chamb'eror manifold. Theu nianiold is *connectedjtoa sourceof flui'dunder pressure and 'to an varc 'extin'fguis'hing` structure. v,The are extinguishing":structure comprises a y rst and. a second arcchute.'V Thesec'ond "arcjnchutefco- 'operates with the .eyeing Lwinnaarste @amature tinguishes they 'arc clear the circuit.' l u l In addition,the chutes are so; arranged'thatif the back pressure developed inthe'rst arc chute renders4 that `are,` chute",inor'ueratve', the hackpressure ,established will `tend to extinguishjthe are in the second,arc chute, and'vicevers'afkk v`A pjair ofnozz'les 'Arnay be, providedrbetween if vthe IFirst are chute" 'iailsjto ,tac'ts and the initialblast, the second. nozzle ,may Y claims. (c1. 20,044,148)

, i ,40. a completebackup or standby breaker,l whichy ex yterr'upft ing,device.

provide .asecond blast of uidto `flow l,through .the second .nozzle andrinto thasecond arc-chute. Byinserting a suitable resistor Y.in thecircuit, `the voltage .recovery rate .of the circuit may be decreased,and if the circuit is not interrupted. by :the rst blast 4of iluidthrough'the first arc chute, it maybe interrupted in the second chutevat a :greatly decreased current. at av much more favorable recovery.frate .by thefvsecond .blastof fluid through the Second arc-chute.`liny this manner, the interrupting .capacity off `th'e circuit vbreaker.for a l.given blast pressure and gas, `consinnptior'i `isf-greatlyfinc'reased.l` u Itk is', thjereioiel one yrolbject.ofi the presentV,iria vention to lprovide a ,newlandimproved 'arc` 1in,-

' Y. Anotherobject.ofgtheinvention isfto provide a Anew and improvedarc,interrupting device lin which an arc chute acts vas astandby tolextinguish krthe are if another 2arc `.chute fails 'to' ,clear the .A.furthrlobject `o'f A,this ,invention is to provide .a- "newv andyimproved are j extinguishing vflslca'ns .which ff utilizes,fluidesirable, back `.pressure inv .one a'rcc'hute to aid inextinguishing .the arc .in .ano'tliery arc chute.,

caused tdloivthrougha second arc'chute only after contact separationandthe initial blast. .5 A still ,further objectl of4 thisinventionjisto,provide .an ,improved l fluid blast circuit "interv,- 'ruptei"` invvwhich a plurality ofja'rc chutesand'gas 'blasts'l extinguish 1afseries ,ofarcs' drawn jb '7a Single movable.farcinadonwt- .f

Obiectsand advantages other than those above As 'forth will befapparentfrom ,the followingdel scription when'read in connectionA withdthe aclconipanying drawinginQwhich; Y,

Figllf cross sec is ,La diagrammatic yshcpvvinlat .partly ini`..-a.lflufid blast circuit brealierem.- esentinvention; y :u Fig'. '.2isy a Viewv .in c' section of the; embvd mento-illustrate Figalvftakenalong fthe line .'Fig. B'isfa view in cross section oftheemlpod-lmentillustra-ted yin Eig-.u l ,takenfalongf Athe-'line The cross blasttype air blast circuit breaker shown by way of examplein11;,comprisesrelatively.,movable arcing contacts, -.such=as:flxed ennetact structure 1 of the nger type and blade-like contact 8. The fixedcontacts structure may comprise a plurality of current carrying contactsand an arcing contact as is well known, and is electrically connected toone line terminal 9 of the breaker, The blade-like movable contact 8 isconnected to the other line terminal I0. Although in general, circuitbreakers of the type considered in Figs. 1, 2 and 3 are provided with aplurality of similar pole structures, one for each phase of a polyphaseelectric circuit, only one such pole structure is shown in the drawingand the circuit breaker will be described in detail as if it were of thesingle pole unit type.

The movable contact 8 is suitably connected to an actuating mechanism(not shown) through a connecting rod I I for operating the movablecontact between closed and open circuit positions.

For the purpose of extinguishing the arcs formed between the contactswhen a power circuit connected thereto is opened, an insulating arcextinguishing structure I2 is arranged with respect to the contacts sothat the arc is drawn at the entrance of the structure directly oppositea gas blast supply conduit I3. The conduit I3 is suitably connectedthrough a blast valve (not shown) to a source of compressed gas, such asair, comprising for example a storage tank and compressor equipment (notshown).

vThe arc extinguishing structure I2 may, for example, comprise a firstarc chute I4 and a second arc chute I5 mounted adjacent to an arc chuteI4.l A fixed arcing contact I9 is mounted between arc chutes I 4 and I5at the upstream end thereof. Arc chutev I5 is so arranged in relation toarc chute I4 that it acts as a standby or backup for arc chute I4, butfunctions cooperatively as well. vThe arc chutes I4 and I 5 may berectangular or circular in form. I

An arc chamber or manifold I 6 of insulating material is arrangedbetween the gas supply conduit I3 and the arc extinguishing structure I2for distributing the fluid under pressure from the point where itarrives in highly concentrated form by the supply conduit I3 to the arcchutes I4 and I5. Arcing contacts 'I and 8 are mounted within manifoldI6 and the arc drawn upon separation of the contacts is enclosed by themanifold upon inception thereof. Manifold I 6 provides a pair of arcingzones 25 and v2li which are located at the upstream end of a pairy ofnozzles I'I and I8, respectively. Nozzles II and I8 direct the iiuidunder pressure from manifold I 6 to arc chutes I4 and I5.

Nozzle II may be so arranged that some fluid under pressure may passtherethrough even when movable arcing contact 8 is in the closedposition, while nozzle I8 maybe arranged similarly to nozzle I 'I or maybe so arranged that the movable arcing contact 8 effectively sealsnozzle I8 until contact 8 has traveled a predetermined distance incontact opening direction.

One end wall of manifold I6,.as illustrated in Fig. 1, defines a passagetherethrough which accommodates the movable sickle-shaped blade contact8. This wall closely surrounds contact 8 and controls the escape ofcompressed air or arc products through passage 20 into the atmosphere. Apluralityr of transversal grooves 2I vprovided in the walls of passage20 tend to establish eddies in the small ow of escaping air and arcproducts through passage 2U and thus minimize the rate of thatnow.

A pair of probe electrodes- 22 and 23 may be mounted within' arc chutesI4 and I5, respectively, for aiding arc extinguishment. A currentlimiting resistor 24 may interconnect electrode 22 and the multiplelinger contacts of the fixed contact structure 'I, thus lowering theValue of the arc current during arc extinguishment.

The circuit breaker illustrated in the drawing is shown with thecooperating arcing contacts in the closed circuit position. An openingoperation is initiated by admission of air under pressure to supplyconduit I3 and manifold I6. As illustrated in Fig. 2, nozzle I'I is openat all times to manifold I6, thus allowing air to iiow through arc chuteI4 substantially simultaneously with its admission to manifold I5. Theflow of air through nozzle I8 and arc chute I5 is at first substantiallyprevented by contact 8, which occupies the entire entrance portion ofnozzle I8 as illustrated in Fig. 3, thus effectively sealing it.

Actuation of the connecting rod I I moves blade contact 8 toward theright to open the electric circuit. As the blade contact 8 is separatedfrom the iixed contact 1, an arc is drawn across the arcing zone 25 ofthe first arc chute I4 and substantially concurrently therewith a pathis opened for blast of air of high intensity through the supply conduitI3, manifold I6, nozzle I'I to the first arc chute I4. Although contact8 does not seal nozzle I'I when in its closed position, it may obstructnozzle I1 sufliciently to prevent a blast of high intensity air fromflowing into nozzle I I and arc chute I4 until after a predeterminedmovement of the contact. This blast includes all the air being suppliedthrough conduit I3, and drives or loops the arc from zone 25 into arcchute I4. The heat of the arc causes vaporization of metal from thecontacts and also causes violent expansion of the air surrounding thearc. The production of the arc thus is accompanied by a virtualexplosion, which tends to reverse the air blast in pipe I3 and chamberI6 by its back pressure.

Frequently the arc is interrupted in the first arc chute by the blast ofair flowing through nozzle Il, at least if the back pressure does notactually reverse the blast. If the arc is lnot al.- ready extinguishedwhen the tip of the blade moves beyond contact I9, the arc islengthenedand divided into a number of serially connected arcs extending betweencontacts 'I, I9 and 8. The second arc chute I5 and nozzle I8 areuncovered upon a predetermined movement 0f contact 8 and at least onepart of the arc is driven or looped from zone 26 into arc chute I5 by aseparate and distinct blast of air from nozzle I8. Thus, a single arc ineach arc chute is acted upon by a separate and distinct air blast.Manifold I6 is large enough so that the blasts may be of substantiallythe same intensity.

In case the explosive or back pressure created in arc chute I4 is greatenough to prohibit extinguishing the arc in that particular chute, thesecond arc chute I5 will cooperate vwith the contacts to act as a backupbreaker to extinguish the arc .and clear. the electric circuit. Eachlarc chute has a common contact system and a. common source of air underpressure, but each arc chute has sufficient interrupting capacity toin,- terrupt the circuit. In fact. the arc chutes are so arranged thatif back pressure in the first arc chute renders that arc chuteinoperative, that back pressure will reduce the air iicw in that arcchute and therefore make an increased air flow available to extinguishthe arc segment in the second arc chute which has a free path toatmosphere. This same operating condition occurs if the second arc chuteis rendered inoperative by back pressure, that back pressure Will reducethe air flow in the second arc chute and help to extinguish the arc inthe first arc chute. Thus, the efficiency of either arc chute isincreased by the back pressure of the other arc chute.

Although but one embodiment of the present invention has beenillustrated and described, it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

It is claimed and desired to secure by Letters Patent:

1. In a fluid blast circuit interrupter, the combination comprising: asource of fluid under pressure, arcing contacts comprising a stationarycontact and a movable contact for establishing an arc, an arcextinguishing structure mounted adjacent said contacts comprising afirst arc chute and a second arc chute, a probe electrode mounted withinsaid ilrst arc chute, a resistor for connecting said probe electrode inseries with said stationary contact, said first arc chute receiving thearc drawn upon initial separation of said contacts and said second arcchute receiving at least a portion of said arc thereafter if said arc isnot extinguished in said first arc chute, and means for providing afirst blast of fluid from said source through said rst arc chuteimmediately before and during separation of said contacts and only afterseparation of said contacts providing a second blast of fluid from saidsource through said second arc chute.

2. In a fluid blast circuit interrupter, the combination comprising: asource of fluid under pressure, a manifold connected to said source forproviding blasts of fluid under pressure, a pair of arcing contactsmounted within said manifold for establishing an arc upon separationthereof comprising a relatively stationary contact and a movablecontact, and an arc extinguishing structure mounted adjacent saidcontacts comprising a first arc chute and a second arc chute bothconnected to said manifold, a probe electrode mounted Within said firstarc chute, a resistor for connecting said probe electrode in series withsaid stationary contact, said ilrst are chute receiving the arc drawnupon initial separ-ation of said contacts and said second arc chutereceiving at least a portion of said arc thereafter if said arc is notextinguished in said rst arc chute. said manifold providing a firstblast of fluid through said first arc chute immediately before andduring separation of said contacts and only after separation of saidcontacts providing a second blast of fluid through said second arcchute.

3. In a fluid blast circuit interrupter, the combination comprising: asource of fluid under pressure, separable arcing contacts for establish-CII ing an arc, a conduit for conveying a blast of fluid from saidsource adjacent said contacts for extinguishing the arc drawn uponseparation of said contacts, an arc extinguishing structure mountedadjacent said contacts comprising a rst arc chute and a second arcchute, a probe electrode mounted Within said rst arc chute, a resistorfor connecting said probe electrode in series with one of said arcingcontacts, an arc chamber surrounding said contacts connecting saidconduit with said arc extinguishing structure for enclosing the arc uponinception thereof, and means comprising a pair of nozzles for directingblasts of iluid from said chamber into said arc chutes, one of saidnozzles directing a irst blast of fluid through said first arc chuteimmediately before and during separation of said contacts and the otherof said nozzles directing a second blast of fluid through said secondarc chute only after separation of said contacts.

4. In a fluid blast circuit interrupter, the comblnation comprising: asource of fluid under pressure, a manifold connected to said source forproviding blasts of fluid under pressure, contact means mounted withinsaid manifold comprising stationary multiple finger contacts and acooperating movable blade Contact for establishing an arc, an arcextinguishing structure mounted adjacent said contacts comprising afirst arc chute and a second arc chute, a probe electrode mounted withinsaid first arc chute, a resistor for connecting said probe electrode inseries with said multiple finger contacts, said first arc chute providedfor extinguishing the arc drawn upon separation of said contacts andsaid second arc chute provided for extinguishing said arc if it existsafter a predetermined movement of said movable contact, and meanscomprising a pair of nozzles one for each of said arc chutes fordirecting blasts of fluid from said manifold into said arc chutes, saidmovable blade contact obstructing the nozzle for said rst arc chute tolimit the ilow of fluid from said source through said first arc chuteuntil said contacts have separated and effectively sealing said nozzlefor said second arc chute until said movable blade contact has traveleda predetermined distance.

GEORGE` A. BURNHAM.

REFEREN CES CITED The following references are of record in the file ofthis patent:

I UNITED STATES PATENTS Number

